The advent of integrated lighting installations, consisting of an ever growing number of individually controllable light sources, lighting devices, luminaires, lighting arrangements and the like with advanced rendering capabilities, may be regarded as transforming lighting systems for both professional and consumer markets. This brings a desire for an intuitive control capable of fully exploiting the rendering capabilities of the complete lighting infrastructure. Several approaches have been proposed to control light sources, lighting devices, luminaires, lighting arrangements and the like.
Optical free space communications, i.e. visible light (VL) and infra-red (IR) communications, for the selection and advanced control of light sources has previously been proposed, and will be referred to as coded light (CL). In general, coded light has been proposed to enable advanced control of light sources. Coded light is based on embedding of data, inter alia invisible identifiers, in the light output of the light sources. Coded light may thus be defined as the embedding of data and identifiers in the light output of a visible light source, wherein the embedded data and/or identifier preferably do not influence the primary lighting function of the light source. Hence, any modulation of the emitted light pertaining to data and/or identifier should be substantially invisible to humans. This allows for applications such as interactive scene setting, commissioning and re-commissioning of networked lighting systems. Coded light may be used in communications applications wherein one or more light sources in a coded lighting system are configured to emit coded light and thereby communicate information to a receiver.
One example for controlling light sources, lighting devices, luminaires, lighting arrangements and the like involves the concept of point and control; this approach exploits the principle of coded light and a remote control unit capable of detecting the code of the light source or luminaire toward which the remote control unit is pointed and thereby to identify the light source or luminaire emitting the coded light. Such a remote control unit typically comprises one or more photodiodes for detecting the coded light emitted by the light source or luminaire. Alternatively the remote control unit may comprise a camera for detecting the coded light. One implementation of the concept of point and control involves having light sources or luminaires sending a unique coded light signal. Different light sources or luminaires send a different signal (i.e. signals with different embedded unique identifiers). One example of signals suitable for this purpose is pulse width modulation (PWM). The point and control approach shows the advantage of using coded light as a mean for a user to be able to select a luminaire by simply pointing the remote control unit towards it. As noted above this approach employs a photodiode in order to detect the coded light message of each luminaire. It has been proposed to detect and decode coded light by means of a standard camera.
European patent application EP11159149.1 relates to a system and method for detecting data embedded into the light output of illumination light detection systems. The light detection system captures light outputted from a scene in a 2D image, and temporal shifted line instances serve as light sample moments. The temporal shift between the capture of consecutive rows on the light detection means during the image capture process gives rise to a line-wise variation in pixel values for those areas in the final captured image of the scene that correspond to parts of the objects that are illuminated with said modulated light source or to the light source itself The line-wise variation in pixel values constitute a pattern of horizontal lines superimposed on top of the image at illuminated objects. The decoding of the message, i.e. the embedded code, in the encoded light requires the recovery of a 1-dimensional (1D) signal that is associated with the original intensity variations of the modulated light source.